# co2 - Alka-SeltzerTM Tablet Chemistry Objective In this...

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Alka-Seltzer TM Tablet Chemistry Objective: In this laboratory exercise you will determine the mass of NaHCO 3 in an Alka-Seltzer tablets to determine experimentally the molecular mass of carbon dioxide, CO 2 , the numerical value of the ideal gas constant (R) and the mass of NaHCO3 in an Alka-Seltzer Tablet. Safety Tips: Wear visorguards at all times while in the laboratory. HANDLE ALL SOLUTIONS WITH CAUTION. If an acid and/or base is spilled on the counter top clean it up immediately. IF A CHEMICAL IS SPILLED ON THE SKIN, IMMEDIATELY RINSE THE AREA WITH LARGE AMOUNTS OF WATER. Dispose of all solutions per instructor's directions. Background: Ideal Gas Law Empirical laws of Boyle’s, Charles, Guy-Lussac and Avogadro’s Principle can describe the behavior of gases. These laws when combined yield the ideal gas law: PV = nRT (1) where P is pressure in atmospheres (atm), V is volume in liters (L), T is temperature in Kelvin (K), n is the number of moles of gas, and R is the universal gas constant which has a value of 0.0821 L atm/K mole for all gases. The number of moles (n) can also be given as moles (n) = sample mass/molecular mass of the gas. Therefore, the ideal gas law can also be written as: PV = (sample mass) RT ________ (2) Molecular Mass The molecular mass (g/mol) of volatile liquid or gas can be determined by the Dumas method, which is an experimental method based on the measurement of the vapor’s density at a given temperature and known pressure. Molecular Mass = (sample mass) RT (3) PV The density (d) of a substance is defined as mass/volume; therefore Equation #3 can be rewritten as Molecular Mass = d RT (4) P

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Determination of NaHCO 3 in the Alka-Seltzer TM 2 The source for carbon dioxide in this laboratory will be an Alka-Seltzer TM tablet. Alka-Seltzer TM tablets are composed of aspirin (acetylsalicylic acid, C 9 H 8 O 4 ), citric acid (H 3 C 6 H 5 O 7 ), sodium bicarbonate (baking soda, NaHCO 3 ) and fillers. When an Alka-Seltzer tablet dissolves in water the following chemical reaction occurs: H 3 C 6 H 5 O 7 (aq) + 3 NaHCO 3 (aq) b 3 H 2 O (l) + 3 CO 2 (g) + Na 3 C 6 H 5 O 7 (aq) (5) (Citric acid) (sodium bicarbonate) (sodium citrate) Sodium bicarbonate ionizes when dissolved in water producing sodium ions (Na + ) and bicarbonate ions (HCO 3 - ). NaHCO
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## This note was uploaded on 07/29/2010 for the course SCI none taught by Professor None during the Spring '10 term at Armstrong State University.

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co2 - Alka-SeltzerTM Tablet Chemistry Objective In this...

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